Free-flowing packaging materials, or "dunnage" or "loose fill" as otherwise known, involve pieces varying greatly in size and shape. That is, some free-flowing dunnages are pieces shaped like peanut shells, while others are rings and still others are other dish-shaped pieces. Whatever the form and material used, the quality of any free-flowing dunnage for packaging purposes is dependent on certain characteristics.
Among the desirable qualities in any free-flowing dunnage material are structural strength, low density and volume maintenance. Ideally the material should also be light in weight, easy to use, versatile for use with any packaged product or with any type of container, non-settling, reusable and static-free, and should prevent movement of products packed within a container and contact between a product's surfaces and interior surfaces of the container.
Foamed plastic materials have dominated the market for free-flowing dunnage, and are made in pieces of various shapes and sizes. Free-flowing dunnage of foamed plastic tends to be light in weight but also tends to have certain disadvantages in handling, such as excessive static problems. Furthermore, environmental concerns have raised considerable questions regarding the use of foamed plastic as a dunnage material, given that plastics which have been used are not biodegradable.
There are many examples of inventions involving plastic free-flowing dunnage, including those disclosed in the following United States patents: U.S. Pat. No. 3,723,240 (Skochdopole et al.), U.S. Pat. No. 3,855,053 (Fuss), and U.S. Pat. No. 3,933,959 (Skochdopole et al.). While free-flowing dunnage of plastic has been most widely used, there are prior disclosures of free-flowing dunnage of other materials, including materials involving use of pulp fiber. However, despite the disadvantages and concerns of using foamed plastic as a free-flowing dunnage material, foamed plastic has continued to dominate in this field.
Among prior disclosures showing use of pulp fiber are U.S. Pat. No. 4,997,091 (McCrea), which teaches manufacture of free-flowing pulp dunnage by extruding pieces of paper fiber and allowing them to dry into solid shapes. However, this material, while it is biodegradable, is disadvantageous in that the heavy weight of solid extruded pulp pieces tends to increase shipping costs unacceptably.
Molded pulp has been used to make containers and other form packaging such as egg cartons and the like. The manufacturing process for such packaging is distinct from the inventions disclosed and claimed herein. And, the molded pulp pieces formed by the method and apparatus of this invention are distinct from anything in the prior art, and form a unique free-flowing pulp fiber dunnage.
Methods for forming molded pulp pieces of the prior art typically include the following steps: First, fiber (such as waste paper) and water are mixed together to produce a pulp slurry. Forming dies are then immersed in the pulp slurry and a vacuum system causes the deposit of pulp fibers thereon. Each forming die includes a screen of suitable mesh such that water of the slurry will be drawn through it leaving a matt of pulp fibers on the screen. A puff of air from the forming die and a vacuum in a transfer die, which mates with the forming die, gently cause the wet formed products to lift off the mold and onto the transfer die. The wet formed products, which typically include about 70-75% water at this stage, are then gently deposited on a conveyor which takes them through a drying oven where hot air is employed to evaporate most of the remaining water content. This process creates molded pulp products which are hollow and generally uniform in shape and size. Such uniformity enables the products to nest with one another, although in some instances molded features may be included to limit or minimize nesting. Published PCT Application WO 91/17932 (Baker et al.), for example, discloses a flowing dunnage made of formed pieces of molded pulp, and discloses the use of particular molded features to limit nesting.
The nesting tendency of molded pulp products is recognized in the Baker et al. disclosure as a particular disadvantage for this sort of dunnage.
Nesting of such dunnage tends to cause loss of volume maintenance within a shipping container filled with such dunnage, thereby providing less effective packaging protection. Nesting also tends to increase the weight-to-volume ratio. Perhaps most significantly, nesting is directly contrary to the free-flowing characteristic which is so essential for such dunnage, which cannot be conveniently used if it is jammed, for example, in an overhead dispensing site.
Methods for making molded pulp products, an old art, vary. Among the variations is that in some cases oven drying is carried out on die-like forms, while in others it is not. In either case, however, mating transfer dies are typically used for transfer of separate, still-moist molded pulp forms from their forming dies to the conveyor for drying. The prior art even recognizes that free-form drying of pulp products can result in significant warpage. See, for example, U.S. Pat. No. 3,185,370 (Reifers et al.). But such warpage effect is viewed as a substantial disadvantage in product manufacture. The prior art does not disclose formation of randomly-shaped edges and voids on a warped product or use of randomness of shape to advantage.
Some comments concerning a variety of other prior art may be appropriate before turning to the invention, even though none of such prior art is considered particularly relevant to the invention disclosed and claimed herein and none of such prior art either discloses or in any way suggests the claimed invention or any significant part of the invention. The disclosures include: